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SIM800C_Hardware_Design_V1.02

Smart Machine Smart Decision

Document Title

SIM800C Hardware Design

Version

V1.02

Date

2015-04-27

Status

Release

Document Control ID

SIM800C_Hardware_Design_V1.02

General Notes
SIMCom offers this information as a service to its customers, to support application and engineering efforts that
use the products designed by SIMCom. The information provided is based upon requirements specifically
provided to SIMCom by the customers. SIMCom has not undertaken any independent search for additional
relevant information, including any information that may be in the customer’s possession. Furthermore, system
validation of this product designed by SIMCom within a larger electronic system remains the responsibility of the
customer or the customer’s system integrator. All specifications supplied herein are subject to change.
Copyright
This document contains proprietary technical information which is the property of SIMCom Limited, copying of
this document and giving it to others and the using or communication of the contents thereof, are forbidden
without express authority. Offenders are liable to the payment of damages. All rights reserved in the event of grant
of a patent or the registration of a utility model or design. All specification supplied herein are subject to change
without notice at any time.
Copyright © Shanghai SIMCom Wireless Solutions Ltd. 2015

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Contents
Version History............................................................................................................ 8
1.

Introduction.......................................................................................................... 9

SIM800C Overview ............................................................................................. 9

2.1.
2.2.
2.3.
2.4.

Package Information ......................................................................................... 13

3.1.
3.2.
3.3.

SIM800C...............................................................................................................................9
SIM800C Key Features.........................................................................................................9
Operating Mode .................................................................................................................. 11
Functional Diagram.............................................................................................................12

Pin Out Diagram .................................................................................................................13
Pin Description....................................................................................................................13
Package Dimensions ...........................................................................................................15

Application Interface......................................................................................... 17

4.1.
4.1.1.
4.1.2.

4.2.
4.2.1.
4.2.2.

4.3.
4.3.1.
4.3.2.
4.3.3.
4.3.4.
4.3.5.

4.4.
4.5.
4.5.1
4.5.2
4.5.3
4.5.4

4.6.
4.7.
4.7.1.
4.7.2.
4.7.3.
4.7.4.

4.8.
4.8.1.

Power Supply ......................................................................................................................17
Power Supply Pin................................................................................................................................ 18
Monitoring Power Supply ................................................................................................................... 19

Power on/off SIM800C.......................................................................................................19
Power on SIM800C............................................................................................................................. 19
Power off SIM800C ............................................................................................................................ 20

Power Saving Mode ............................................................................................................22
Minimum Functionality Mode ............................................................................................................ 22
Sleep Mode 1 (AT+CSCLK=1) .......................................................................................................... 22
Wake Up SIM800C from Sleep Mode 1 ............................................................................................. 23
Sleep Mode 2 (AT+CSCLK=2) .......................................................................................................... 23
Wake Up SIM800C from Sleep Mode 2 ............................................................................................. 23

Power Saving Mode ............................................................................................................23
Serial Port and USB Interface.............................................................................................24
Function of Serial Port ........................................................................................................................ 25
Serial Interfaces................................................................................................................................... 25
Debug Interface................................................................................................................................... 27
Software Upgrade................................................................................................................................ 28

UART1_RI Behaviors.........................................................................................................28
Audio Interfaces..................................................................................................................29
Speaker Interfaces Configuration........................................................................................................ 30
Microphone Interfaces Configuration ................................................................................................. 30
Audio Electronic Characteristic .......................................................................................................... 30
TDD .................................................................................................................................................... 31

SIM Card Interface..............................................................................................................31
SIM Card Application ......................................................................................................................... 31

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4.8.2.
4.8.3.

SIM Card Design Guide...................................................................................................................... 32
Design Considerations for SIM Card Holder ...................................................................................... 32

4.9. ADC ....................................................................................................................................34
4.10. Network Status Indication...................................................................................................35
4.10.1.

NETLIGHT Multiplexing Function................................................................................................. 35

4.11. Operating Status Indication.................................................................................................36
4.11.1.

STATUS Multiplexing Function ...................................................................................................... 36

4.12. RF Synchronization Signal .................................................................................................36
4.12.1.

RF_SYNC Multiplexing Function................................................................................................... 36

4.13. Antenna Interface................................................................................................................37
4.13.1
4.13.2

GSM Antenna Interface ................................................................................................................... 37
Bluetooth Antenna Interface ............................................................................................................ 38

PCB Layout ........................................................................................................ 39

5.1
5.2

Pin Assignment ...................................................................................................................39
Principle of PCB Layout .....................................................................................................39

5.2.1
5.2.2
5.2.3
5.2.4
5.2.5

Antenna Interface ................................................................................................................................ 40
Power Supply ...................................................................................................................................... 40
SIM Card Interface.............................................................................................................................. 40
Audio Interface.................................................................................................................................... 40
Others .................................................................................................................................................. 40

Electrical, Reliability and Radio Characteristics ........................................... 41

6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
6.10
6.10.1
6.10.2
6.10.3

I.
II.

Module RF Output Power................................................................................................................ 44
Module RF Receive Sensitivity ....................................................................................................... 45
Module Operating Frequencies........................................................................................................ 45

Manufacturing ................................................................................................... 46

7.1.
7.2.
7.3.
7.4.

Absolute Maximum Ratings ...............................................................................................41
Recommended Operating Conditions .................................................................................41
Digital Interface Characteristics..........................................................................................41
SIM Card Interface Characteristics.....................................................................................41
SIM_VDD Characteristics ..................................................................................................42
VDD_EXT Characteristics .................................................................................................42
VRTC Characteristics .........................................................................................................42
Current Consumption (VBAT=4.0V) .................................................................................42
Electro-Static Discharge .....................................................................................................43
Radio Characteristics ..........................................................................................................44

Top and Bottom View of SIM800C....................................................................................46
Typical Solder Reflow Profile ............................................................................................46
The Moisture Sensitivity Level...........................................................................................47
Baking Requirements..........................................................................................................47

Appendix............................................................................................................. 48
Related Documents .............................................................................................................48
Multiplexing Function.........................................................................................................49

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III.
IV.

Terms and Abbreviations ....................................................................................................49
Safety Caution.....................................................................................................................51

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Table Index
TABLE 1: MODULE INFORMATION ............................................................................................................................. 9
TABLE 2: SIM800C KEY FEATURES ............................................................................................................................. 9
TABLE 3: CODING SCHEMES AND MAXIMUM NET DATA RATES OVER AIR INTERFACE ............................ 11
TABLE 4: OVERVIEW OF OPERATING MODES........................................................................................................ 11
TABLE 5: PIN DESCRIPTION ....................................................................................................................................... 13
TABLE 6: RECOMMENDED ZENER DIODE .............................................................................................................. 17
TABLE 7: THE CURRENT CONSUMPTION OF FUNCTION MODE ........................................................................ 22
TABLE 8: SERIAL PORT AND USB PIN DEFINITION ............................................................................................... 24
TABLE 9: SERIAL PORT CHARACTERISTICS........................................................................................................... 25
TABLE 10: USB_VBUS OPERATION VOLTAGE ........................................................................................................ 27
TABLE 11: RI BEHAVIORS ........................................................................................................................................... 28
TABLE 12: AUDIO INTERFACE DEFINITION............................................................................................................ 29
TABLE 13: MICROPHONE INPUT CHARACTERISTICS........................................................................................... 30
TABLE 14: AUDIO OUTPUT CHARACTERISTICS .................................................................................................... 31
TABLE 15: SIM PIN DEFINITION................................................................................................................................. 31
TABLE 16: PIN DESCRIPTION (MOLEX SIM CARD HOLDER) .............................................................................. 33
TABLE 17: PIN DESCRIPTION (AMPHENOL SIM CARD HOLDER)....................................................................... 34
TABLE 18: PIN DEFINITION OF THE ADC................................................................................................................. 34
TABLE 19: ADC SPECIFICATION ................................................................................................................................ 35
TABLE 20: PIN DEFINITION OF THE NETLIGHT ..................................................................................................... 35
TABLE 21: STATUS OF THE NETLIGHT PIN.............................................................................................................. 35
TABLE 22: NETLIGHT MULTIPLEXING FUNCTION................................................................................................ 35
TABLE 23: PIN DEFINITION OF THE STATUS........................................................................................................... 36
TABLE 24: STATUS MULTIPLEXING FUNCTION ..................................................................................................... 36
TABLE 25: DEFINITION OF THE RF_SYNC PIN........................................................................................................ 36
TABLE 26: RF_SYNC MULTIPLEXING FUNCTION.................................................................................................. 36
TABLE 27: ABSOLUTE MAXIMUM RATINGS........................................................................................................... 41
TABLE 28: RECOMMENDED OPERATING CONDITIONS ....................................................................................... 41
TABLE 29: DIGITAL INTERFACE CHARACTERISTICS ........................................................................................... 41
TABLE 30: SIM CARD INTERFACE CHARACTERISTICS........................................................................................ 41
TABLE 31: SIM_VDD CHARACTERISTICS................................................................................................................ 42
TABLE 32: VDD_EXT CHARACTERISTICS ............................................................................................................... 42
TABLE 33: VRTC CHARACTERISTICS ....................................................................................................................... 42
TABLE 34: CURRENT CONSUMPTION ...................................................................................................................... 42
TABLE 35: THE ESD CHARACTERISTICS (TEMPERATURE: 25℃, HUMIDITY: 45 %) ....................................... 43
TABLE 36: GSM850 AND EGSM900 CONDUCTED RF OUTPUT POWER.............................................................. 44
TABLE 37: DCS1800 AND PCS1900 CONDUCTED RF OUTPUT POWER............................................................... 44
TABLE 38: CONDUCTED RF RECEIVE SENSITIVITY ............................................................................................. 45
TABLE 39: OPERATING FREQUENCIES..................................................................................................................... 45
TABLE 40: MOISTURE SENSITIVITY LEVEL AND FLOOR LIFE ........................................................................... 47
TABLE 41: BAKING REQUIREMENTS ....................................................................................................................... 47
TABLE 42: RELATED DOCUMENTS ........................................................................................................................... 48
TABLE 43: MULTIPLEXING FUNCTION .................................................................................................................... 49
TABLE 44: TERMS AND ABBREVIATIONS................................................................................................................ 49
TABLE 45: SAFETY CAUTION..................................................................................................................................... 51
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Figure Index
FIGURE 1: SIM800C FUNCTIONAL DIAGRAM......................................................................................................... 12
FIGURE 2: PIN OUT DIAGRAM (TOP VIEW) ............................................................................................................. 13
FIGURE 3: DIMENSIONS OF SIM800C (UNIT: MM) ................................................................................................. 15
FIGURE 4: RECOMMENDED PCB FOOTPRINT OUTLINE (UNIT: MM) ................................................................ 16
FIGURE 5: REFERENCE CIRCUIT OF THE VBAT INPUT......................................................................................... 17
FIGURE 6: REFERENCE CIRCUIT OF THE LDO POWER SUPPLY ......................................................................... 17
FIGURE 7: REFERENCE CIRCUIT OF THE DC-DC POWER SUPPLY..................................................................... 18
FIGURE 8: VBAT VOLTAGE DROP DURING TRANSMIT BURST........................................................................... 18
FIGURE 9: THE MINIMAL VBAT VOLTAGE REQUIREMENT AT VBAT DROP .................................................... 18
FIGURE 10: POWERED ON/DOWN MODULE USING TRANSISTOR..................................................................... 19
FIGURE 11: POWERED ON/DOWN MODULE USING BUTTON ............................................................................. 19
FIGURE 12: TIMING OF POWER ON MODULE......................................................................................................... 19
FIGURE 13: TIMING OF POWER OFF SIM800C BY PWRKEY ................................................................................ 20
FIGURE 14: TIMING OF RESTART SIM800C.............................................................................................................. 22
FIGURE 15: RTC SUPPLY FROM CAPACITOR........................................................................................................... 23
FIGURE 16: RTC SUPPLY FROM NON-CHARGEABLE BATTERY ......................................................................... 24
FIGURE 17: RTC SUPPLY FROM RECHARGEABLE BATTERY .............................................................................. 24
FIGURE 18: CONNECTION OF THE SERIAL INTERFACES..................................................................................... 26
FIGURE 19: RESISTOR MATCHING CIRCUIT ........................................................................................................... 26
FIGURE 20 : DIODE ISOLATION CIRCUIT................................................................................................................. 26
FIGURE 21: TX LEVEL MATCHING CIRCUIT ........................................................................................................... 27
FIGURE 22: RX LEVEL MATCHING CIRCUIT........................................................................................................... 27
FIGURE 23: USB REFERENCE CIRCUIT .................................................................................................................... 27
FIGURE 24: CONNECTION FOR SOFTWARE UPGRADING AND DEBUGGING.................................................. 28
FIGURE 25: UART1_RI BEHAVIOUR OF VOICE CALLING AS A RECEIVER ....................................................... 29
FIGURE 26: UART1_RI BEHAVIOUR OF URC OR RECEIVE SMS.......................................................................... 29
FIGURE 27: UART1_RI BEHAVIOUR AS A CALLER................................................................................................. 29
FIGURE 28: SPEAKER REFERENCE CIRCUIT .......................................................................................................... 30
FIGURE 29: MICROPHONE REFERENCE CIRCUIT.................................................................................................. 30
FIGURE 30: REFERENCE CIRCUIT OF THE 8-PIN SIM CARD HOLDER............................................................... 32
FIGURE 31: REFERENCE CIRCUIT OF THE 6-PIN SIM CARD HOLDER............................................................... 32
FIGURE 32: MOLEX 91228 SIM CARD HOLDER ...................................................................................................... 33
FIGURE 33: AMPHENOL C707 10M006 512 SIM CARD HOLDER........................................................................... 34
FIGURE 34: REFERENCE CIRCUIT OF NETLIGHT .................................................................................................. 35
FIGURE 35: RF_SYNC SIGNAL DURING TRANSMIT BURST ................................................................................ 36
FIGURE 36: GSM ANTENNA MATCHING CIRCUIT ................................................................................................. 37
FIGURE 37: GSM ANTENNA MATCHING CIRCUIT WITHOUT RF CONNECTOR ............................................... 37
FIGURE 38: BLUETOOTH ANTENNA MATCHING CIRCUIT .................................................................................. 38
FIGURE 39: PIN ASSIGNMENT.................................................................................................................................... 39
FIGURE 40: TOP AND BOTTOM VIEW OF SIM800C ................................................................................................ 46
FIGURE 41: TYPICAL SOLDER REFLOW PROFILE OF LEAD-FREE PROCESSES.............................................. 46

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Version History
Date

Version

Description of change

Author

2014-11-06

1.00

Origin

Yanwu.wang;
Xiaobo.bai

2015-01-06

1.01

Update figure1,figure12,figure40
Delete figure26
Add VRTC segment to table5
Update table11,table34,table35,table36

Yanwu.wang;
Xiaobo.bai

2015-04-27

1.02

Update figure7,figure10,figure11,figure10,figure12,figure13,
figure14,figure23,figure37,figure38
Update table1,table2

Yanwu.wang;
Xiaobo.bai

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1. Introduction
This document describes SIM800C hardware interface in great detail. The document can help customer to
quickly understand SIM800C interface specifications, electrical and mechanical details. With the help of this
document and other SIM800C application notes, customer guide, customers can use SIM800C to design various
applications quickly.

2. SIM800C Overview
SIM800C is a quad-band GSM/GPRS module that works on frequencies GSM850MHz, EGSM900MHz,
DCS1800MHz and PCS1900MHz. SIM800C features GPRS multi-slot class10/class12 (optional) and supports
the GPRS coding schemes CS-1, CS-2, CS-3 and CS-4.
With a tiny configuration of 17.6*15.7*2.3mm, SIM800C can meet almost all the space requirements in
customers’ applications, such as smart phone, PDA and other mobile devices.
SIM800C is a SMT package with 42 pads, and provides all hardware interfaces between the module and
customers’ boards.

One 3 lines serial port and one full modem serial port;

One USB, the USB interface can debug, download software;

One audio channel which include a microphone input and a speaker output;

Programmable general purpose input and output;

One SIM card interface;

Support Bluetooth (need software support).
SIM800C is designed with power saving technique so that the current consumption is as low as 0.6mA in sleep
mode.

2.1. SIM800C
Table 1: Module information
SIM800C
GSM

850,900,1800 and 1900MHz

(need software support)

FLASH

SIM800C (24Mbit)
SIM800C32 (32Mbit)

RAM

32Mbit

2.2. SIM800C Key Features
Table 2: SIM800C key features
Feature

Implementation

Power supply

3.4V ~4.4V

Power saving

Typical power consumption in sleep mode is 0.88mA (BS-PA-MFRMS=9 )

Frequency bands



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Quad-band: GSM 850, EGSM 900, DCS 1800, PCS 1900. SIM800C can
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

search the 4 frequency bands automatically. The frequency bands can also be
set by AT command “AT+CBAND”. For details, please refer to document [1].
Compliant to GSM Phase 2/2+

Transmitting power




Class 4 (2W) at GSM 850 and EGSM 900
Class 1 (1W) at DCS 1800 and PCS 1900

GPRS connectivity




GPRS multi-slot class 12（default）
GPRS multi-slot class 1~12 (option)

Temperature range




Normal operation: -40°C ~ +85°C
Storage temperature -45°C ~ +90°C

Data GPRS








GPRS data downlink transfer: max. 85.6 kbps
GPRS data uplink transfer: max. 85.6 kbps
Coding scheme: CS-1, CS-2, CS-3 and CS-4
PAP protocol for PPP connect
Integrate the TCP/IP protocol.
Support Packet Broadcast Control Channel (PBCCH)

USSD



Unstructured Supplementary Services Data (USSD) support

SMS




MT, MO, CB, Text and PDU mode
SMS storage: SIM card

SIM interface

Support SIM card: 1.8V, 3V

External antenna

Antenna pad

Audio features

Speech codec modes:
 Half Rate (ETS 06.20)
 Full Rate (ETS 06.10)
 Enhanced Full Rate (ETS 06.50 / 06.60 / 06.80)
 Adaptive multi rate (AMR)
 Echo Cancellation
 Noise Suppression

Serial port and
USB port










Serial port:
Default one Full modem serial port
Can be used for AT commands or data stream
Support RTS/CTS hardware handshake and software ON/OFF flow control
Multiplex ability according to GSM 07.10 Multiplexer Protocol
Autobauding supports baud rate from 1200 bps to 115200bps
upgrading firmware
USB port:
USB_DN and USB_DP
Can be used for debugging and upgrading firmware

Phonebook management

Support phonebook types: SM, FD, LD, RC, ON, MC

SIM application toolkit

GSM 11.14 Release 99

Physical characteristics

Size:17.6*15.7*2.3mm
Weight:1.3g

Firmware upgrade

Full modern serial port or USB port(recommend to use USB port)

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Table 3: Coding schemes and maximum net data rates over air interface
Coding scheme

1 timeslot

2 timeslot

4 timeslot

CS-1

9.05kbps

18.1kbps

36.2kbps

CS-2

13.4kbps

26.8kbps

53.6kbps

CS-3

15.6kbps

31.2kbps

62.4kbps

CS-4

21.4kbps

42.8kbps

85.6kbps

2.3. Operating Mode
The table below summarizes the various operating modes of SIM800C.
Table 4: Overview of operating modes
Mode

Normal
operation

Function

GSM/GPRS
SLEEP

Module will automatically go into sleep mode if the conditions of sleep
mode are enabling and there aren’t on air and hardware interrupt (such as
GPIO interrupt or data on serial port).
In this case, the current consumption of module will reduce to the minimal
level.
In sleep mode, the module can still receive paging message and SMS.

GSM
IDLE

Software is active. Module is registered to the GSM network, and the
module is ready to communicate.

GSM
TALK

Connection between two subscribers is in progress. In this case, the power
consumption depends on network settings such as DTX off/on,
FR/EFR/HR, hopping sequences, antenna.

GPRS
STANDBY

Module is ready for GPRS data transfer, but no data is currently sent or
received. In this case, power consumption depends on network settings and
GPRS configuration.

GPRS
DATA

There is GPRS data transfer (PPP or TCP or UDP) in progress. In this case,
power consumption is related with network settings (e.g. power control
level); uplink/downlink data rates and GPRS configuration (e.g. used
multi-slot settings).

Power off

Normal power off by sending AT command “AT+CPOWD=1” or using the PWRKEY. The
power management unit shuts down the power supply for the baseband part of the module.
Software is not active. The serial port is not accessible. Power supply (connected to VBAT)
remains applied.

Minimum
functionality
mode

AT command “AT+CFUN” can be used to set the module to a minimum functionality mode
without removing the power supply. In this mode, the RF part of the module will not work
or the SIM card will not be accessible, or both RF part and SIM card will be closed, and the
serial port is still accessible. The power consumption in this mode is lower than normal
mode.

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2.4. Functional Diagram
The following figure shows a functional diagram of SIM800C:

GSM baseband

GSM RF

Antenna interface

Other interface

P ow er
S upply

P ow er m anagem ent unit

G SM

Radio
Frequency

R TC

D igitalInterface

A nalog Interface

UART

Audio
A nalog base
band
AD C

D igitalbase
band

S IM
U SB
G P IO

Figure 1: SIM800C functional diagram

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3. Package Information
3.1. Pin Out Diagram

Figure 2: Pin out Diagram (Top view)

3.2. Pin Description
Table 5: Pin description
Pin name

Pin number

I/O

Description

34,35

Power supply

Comment

Power supply
VBAT

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VRTC

I/O

Power supply for RTC

It is recommended to
connect with a battery or a
capacitor (e.g. 4.7uF).

VDD_EXT

2.8V power output

If these pins are unused,
keep open.

GND

8,13,19,21,27,30,
31,33,36,37

Ground

GND for VBAT recommend
to use 36,37pin

PWRKEY should be pulled low at
least 1 second and then released to
power on/down the module.

Internally
VBAT.

Differential audio input

Differential audio output

Power on/down
PWRKEY

pulled

Audio interfaces
MICP

MICN

SPKP

SPKN

If these pins are unused,
keep open.

GPIO
NETLIGHT

Network status

STATUS

Power on status

UART1_DTR

Data terminal ready

UART1_RI

Ring indicator

UART1_DCD

Data carrier detect

UART1_CTS

Clear to send

UART1_RTS

Request to send

UART1_TXD

Transmit data

UART1_RXD

Receive data

UART2_TXD

Transmit data

UART2_RXD

Receive data

USB_VBUS

USB_DP

I/O

USB_DN

I/O

Serial port

If these pins are unused,
keep open.

Debug interface
Debug and download

If these pins are unused,
keep open.

10bit general analog to digital
converter

If these pins are unused,
keep open.

ADC
ADC

SIM card interface
SIM_VDD

Voltage supply for SIM card.
Support 1.8V or 3V SIM card

SIM_DATA

I/O

SIM data input/output

SIM_CLK

SIM clock

SIM_RST

SIM reset

SIM_DET

SIM card detection

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All signals of SIM interface
should be protected against
ESD with a TVS diode
array.
If these pins are unused,
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keep open.
Antenna interface
GSM_ANT

I/O

Connect GSM antenna

BT_ANT

I/O

Connect Bluetooth antenna

Synchronizing signal of RF

Synchronizing signal of RF
RF_SYNC

3.3. Package Dimensions

Figure 3: Dimensions of SIM800C (Unit: mm)

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Figure 4: Recommended PCB footprint outline (Unit: mm)

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4. Application Interface
4.1. Power Supply
The power supply range of SIM800C is from 3.4V to 4.4V. Recommended voltage is 4.0V. The transmitting
burst will cause voltage drop and the power supply must be able to provide sufficient current up to 2A. For the
VBAT input, a bypass capacitor (low ESR) such as a 100 µF is strongly recommended.
For the VBAT input, a 100uF Tantalum capacitor (CA low ESR) and a 1uF~10uF Ceramics capacitor CB are
strongly recommended. Increase the 33pF and 10pF capacitors can effectively eliminate the high frequency
interference. A 5.1V/500mW Zener diode is strongly recommended, the diode can prevent chip from damaging
by the voltage surge. These capacitors and Zener diode should be placed as close as possible to SIM800C
VBAT pins.
VBAT

33pF 10pF

5.1V
500m W

Figure 5: Reference circuit of the VBAT input
Table 6: Recommended zener diode
Vendor

Part number

Power(watts)

Packages

On semi

MMSZ5231BT1G

500mW

SOD123

Prisemi

PZ3D4V2H

500mW

SOD323

Vishay

MMSZ4689-V

500mW

SOD123

Crownpo

CDZ55C5V1SM

500mW

0805

The following figure is the reference design of +5V input power supply. The output power supply is 4.1V, thus a
linear regulator can be used.
U 101 M IC 29302
2
C 101
100uF

C 102
1uF

V out

V in
O n/O ff

P W R _C T R L

GND

D C IN P U T

VBAT

4
5

R 101
100K

C 103

C 104

330uF

100nF

R 103
470Ω

R 102
43K

Figure 6: Reference circuit of the LDO power supply
If there is a high drop-out between the input and the desired output (VBAT), a DC-DC power supply will be
preferable because of its better efficiency especially with the 2A peak current in burst mode of the module. The
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following figure is the reference circuit.

+ C 102

C 101
100uF

1uF

O n/O ff

P W R _C T R L

GND

U 101 LM 2596-A D J
1
2
V in
V out

D C input

L101

C 103

VBAT

270Ω

100uH
D 102

330uF
M B R 360

F B 101

C 104
100nF

R 101
2.2K
R 102
1K

Figure 7: Reference circuit of the DC-DC power supply
The single 3.7V Li-ion cell battery can be connected to SIM800C VBAT pins directly. But the Ni-Cd or Ni-MH
battery must be used carefully, since their maximum voltage can rise over the absolute maximum voltage of the
module and damage it.
When battery is used, the total impedance between battery and VBAT pins should be less than 150mΩ.
The following figure shows the VBAT voltage drop at the maximum power transmit phase, and the test condition
is as following:
VBAT=4.0V,
A VBAT bypass capacitor CA=100µF tantalum capacitor (ESR=0.7Ω),
Another VBAT bypass capacitor CB=1uF~10uF.
577us

4.615m s

B urst:2A

IV B A T
VBAT

M ax:350m V

Figure 8: VBAT voltage drop during transmit burst
4.1.1.

Power Supply Pin

Pin34 and Pin35 are VBAT input, Pin36 and Pin37 are GND of power supply, and VRTC pin is power supply of
the RTC circuit in the module. VDD_EXT output 2.8V when module is in normal operation mode.
When designing the power supply in customers’ application, pay special attention to power losses. Ensure that
the input voltage never drops below 3.0V even when current consumption rises to 2A in the transmit burst. If the
power voltage drops below 3.0V, the module may be shut down automatically. The PCB traces from the VBAT
pins to the power supply must be wide enough (at least 60mil) to decrease voltage drops in the transmit burst.
The power IC and the bypass capacitor should be placed to the module as close as possible.
VBAT
M IN :3.0V

Figure 9: The minimal VBAT voltage requirement at VBAT drop
Note: Hardware power off voltage is 3.0V.
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4.1.2.

Monitoring Power Supply

AT command “AT+CBC” can be used to monitor the VBAT voltage. For detail, please refer to document [1].

4.2. Power on/off SIM800C
4.2.1.

Power on SIM800C

Customer can power on SIM800C by pulling down the PWRKEY pin for at least 1 second and release. This pin
is already pulled up to VBAT in the module internal, so external pull up is not necessary. Reference circuits are
shown as below.

100K

P ow er
on/off logic

PW R KEY

4.7K
T urn on/off
im pulse

M odule

47K

Figure 10: Powered on/down module using transistor
3V

100K
PW R KEY

P ow er
on/off logic

M odule

Figure 11: Powered on/down module using button

The power on timing is illustrated as in the following figure.

VBAT
PW R KEY
(IN P U T )

T >1.5s
t>1s
V IL<0.7V
T >55m s

V D D _E X T

t>3s

S TA TU S
S erialP ort

U ndefind

A ctive

Figure 12: Timing of power on module
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When power on procedure is completed, SIM800C will send following URC to indicate that the module is ready
to operate at fixed baud rate.
RDY
This URC does not appear when autobauding function is active.
Note: Customer can use AT command “AT+IPR=x” to set a fixed baud rate and save the configuration to
non-volatile flash memory. After the configuration is saved as fixed baud rate, the Code “RDY” should be
received from the serial port every time when SIM800C is powered on. For details, please refer to the chapter
“AT+IPR” in document [1].
4.2.2.

Power off SIM800C

SIM800C will be powered off in the following situations：
 Normal power off procedure: power off SIM800C by the PWRKEY pin.
 Normal power off procedure: power off SIM800C by AT command “AT+CPOWD=1”.
 Abnormal power off: over-voltage or under-voltage automatic power off.
 Abnormal power off: over-temperature or under-temperature automatic power off.
4.2.2.1.

Power off SIM800C by the PWRKEY Pin

Customer can power off SIM800C by pulling down the PWRKEY pin for at least 1 second and release. Please
refer to the power on circuit. The power off timing is illustrated in the following figure.
1s2s；
If 2s≤T1<33s，T2>T1+55ms
This procedure makes the module log off from the network and allows the software to enter into a secure state to
save data before completely shut down.
Before the completion of the power off procedure, the module will send URC:
NORMAL POWER OFF
At this moment, AT commands can not be executed any more. Power off mode can also be indicated by STATUS
pin, which is at low level at this time.
4.2.2.2.

Power off SIM800C by AT Command

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SIM800C can be powered off by AT command “AT+CPOWD=1”. This procedure makes the module log off from
the network and allows the software to enter into a secure state to save data before completely shut down.
Before the completion of the power off procedure, the module will send URC:
NORMAL POWER OFF
At this moment, AT commands can not be executed any more. Power off mode can also be indicated by STATUS
pin, which is at low level at this time.
For detail about AT command “AT+CPOWD”, please refer to document [1].
4.2.2.3.

Over-Voltage or Under-Voltage Power off

The module software monitors the VBAT voltage constantly.
If the voltage ≤ 3.5V, the following URC will be reported:
UNDER-VOLTAGE WARNNING
If the voltage ≥ 4.3V, the following URC will be reported:
OVER-VOLTAGE WARNNING
If the voltage < 3.4V, the following URC will be reported, and the module will be automatically powered off.
UNDER-VOLTAGE POWER OFF
If the voltage > 4.4V, the following URC will be reported, and the module will be automatically powered off.
OVER-VOLTAGE POWER OFF
At this moment, AT commands can not be executed any more. Power off mode can also be indicated by STATUS
pin, which is at low level at this time.
4.2.2.4.

Over-Temperature or Under-Temperature Power off

The module will constantly monitor the temperature of the module,
If the temperature ≥ +80℃, the following URC will be reported:
+CMTE: 1
If the temperature ≤ -30℃, the following URC will be reported:
+CMTE:-1
If the temperature > +85℃, the following URC will be reported, and the module will be automatically powered
off.
+CMTE: 2
If the temperature < -40℃, the following URC will be reported, and the module will be automatically powered
off.
+CMTE:-2
At this moment, AT commands can not be executed any more. Power off mode can also be indicated by STATUS
pin, which is at low level at this time.
Note：The default temperature detect is disable, AT command “AT+CMTE” could be used to read the
temperature when the module is running.For details please refer to document [1].
4.2.2.5.

Restart SIM800C by PWRKEY Pin:

When the module works normally, if the customer wants to restart the module, follow the procedure below:
1) Power off the module.
2) Wait for at least 800ms after STATUS pin changed to low level.
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Power on the module.
T 3 >800m s

1s“can be used to
set SIM800C into minimum functionality. When SIM800C is in sleep mode and minimum functionality mode,
the current of module is lowest.
4.3.1.

Minimum Functionality Mode

There are three functionality modes, which could be set by AT command “AT+CFUN=“. The command
provides the choice of the functionality levels =0, 1, 4.
 AT+CFUN=0： Minimum functionality.
 AT+CFUN=1： Full functionality (default).
 AT+CFUN=4： Flight mode (disable RF function).
Table 7: The current consumption of Function Mode

Current consumption(mA) (sleep mode)

0.6

0.88

0.65

Minimum functionality mode minimizes the current consumption to the lowest level. If SIM800C is set to
minimum functionality by “AT+CFUN=0”, the RF function and SIM card function will be disabled. In this
case, the serial port is still accessible, but partial AT commands and correlative to RF function and SIM card
function will not be accessible.
For detailed information about AT command “AT+CFUN=“, please refer to document [1].
4.3.2.

Sleep Mode 1 (AT+CSCLK=1)

Customer can control SIM800C module to enter or exit the sleep mode (AT+CSCLK=1) by DTR signal. When
DTR is in high level and without interrupt (on air and hardware such as GPIO interrupt or data in serial port),
SIM800C will enter sleep mode automatically. In this mode, SIM800C can still receive paging or SMS from
network but the serial port is not accessible.

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4.3.3.

Wake Up SIM800C from Sleep Mode 1

When SIM800C is in sleep mode 1(AT+CSCLK=1), the following methods can wake up the module:
 Pull down DTR pin.
The serial port will be active after DTR pin is pulled to low level for about 50ms.
 Receive a voice or data call from network.
 Receive a SMS from network.
 Receive external interrupt.
Note: After module has received incoming call or new SMS, serial port can report URC, but the serial port can
not input AT command. Only after the DTR pin is pulled to low level for 50ms, the serial port can input AT
command.
4.3.4.

Sleep Mode 2 (AT+CSCLK=2)

In this mode, SIM800C will continuously monitor the serial port data signal. When there is no data transfer over 5
seconds on the RXD signal and there is no on air and hardware interrupts (such as GPIO interrupt), SIM800C will
enter sleep mode 2 automatically. In this mode, SIM800C can still receive paging or SMS from network.
4.3.5.

Wake Up SIM800C from Sleep Mode 2

When SIM800C is in sleep mode 2 (AT+CSCLK=2), the following methods can wake up the module:
 Send data to SIM800C via main serial port (the first character will lose).
 Receive a voice or data call from network.
 Receive a SMS from network.
Note: Autobauding is default. It cannot enter sleep mode in the absence of synchronous serial port baud rate
after module power on.

4.4. Power Saving Mode
Current input for RTC when the VBAT is not supplied for the system. Current output for backup battery when
the VBAT power supply is in present and the backup battery is in low voltage state. The RTC power supply of
module can be provided by an external capacitor or a battery (non-chargeable or rechargeable) through the VRTC.
The following figures show various reference circuits for RTC back up.


External capacitor backup

M odule
V R TC

1.5K

Large-capacitance
C apacitor

R TC
C ore

Figure 15: RTC supply from capacitor


Non-chargeable battery backup

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M odule
V R TC

1.5K

R TC
C ore

N on-chargeable
B ackup B attery

Figure 16: RTC supply from non-chargeable battery


Rechargeable battery backup

M odule
V R TC

1.5K

R echargeable
B ackup B attery

R TC
C ore

Figure 17: RTC supply from rechargeable battery
Note: When shut off VBAT and power on VRTC only, the clock error becomes larger.

4.5. Serial Port and USB Interface
SIM800C default provides one unbalanced asynchronous serial ports. The module is designed as a DCE (Data
Communication Equipment). The following figure shows the connection between module and client (DTE).
Table 8: Serial port and USB pin definition

Serial port

Debug port

Pin name

Pin number

Function

UART1_DTR

Data terminal ready

UART1_RI

Ring indicator

UART1_DCD

Data carrier detect

UART1_CTS

Clear to send

UART1_RTS

Request to send

UART1_TXD

Transmit data

UART1_RXD

Receive data

UART2_TXD

Transmit data

UART2_RXD

Receive data

USB_VBUS

USB power supply

USB_DP

D+ data input/output

USB_DN

D- data input/output

Note: Hardware flow control is disabled by default. AT command “AT+IFC=2, 2”can enable hardware flow
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control. AT command “AT+IFC=0,0”can disable hardware flow control. For more details please refer to
document [1].
Table 9: Serial port characteristics
Symbol

Min

Max

Unit

VIL

-0.3

0.7

VIH

2.1

3.1

VOL

0.4

VOH

2.4

4.5.1

Function of Serial Port

Serial port:
 Full mode device.
 Contain data lines UART1_TXD/UART1_RXD, hardware flow control lines UART1_RTS/UART1_CTS,
status lines UART1_DTR、UART1_DCD and UART1_RI.
 Serial port can be used for GPRS service and AT communication. It can also be used for multiplexing
function. For details about multiplexing function, please refer to table 11.
 Autobauding supports the following baud rates:
1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200bps
Autobauding allows SIM800C to automatically detect the baud rate of the host device. Pay more attention to the
following requirements:
 Synchronization between DTE and DCE:
When DCE powers on with autobauding enabled, it is recommended to send "AT" or "at" or "aT" or "At"
to synchronize the baud rate, until DTE receives the "OK" response, which means DTE and DCE are
correctly synchronized. For more information please refer to AT command "AT+IPR".
 Restrictions of autobauding operation:
The DTE serial port must be set at 8 data bits, no parity and 1 stop bit.
The URC such as "RDY", "+CFUN: 1" and "+CPIN: READY” will not be reported.
Note: Customer can use AT command “AT+IPR=x” to set a fixed baud rate and the setting will be saved to
non-volatile flash memory automatically. After the configuration is set as fixed baud rate, the URC such as
"RDY", "+CFUN: 1" and "+CPIN: READY” will be reported when SIM800C is powered on.
4.5.2

Serial Interfaces

The following figure shows the connection between module and client (DTE).

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M odule(D C E )
S erialP ort

C ustom er(D T E )
S erialP ort

U A R T1_T X D

TX D

U A R T1_R X D

RXD

U A R T1_R T S

R TS

U A R T1_C T S

C TS

U A R T1_D T R

D TR

U A R T1_D C D

DCD

U A R T1_R I

R IN G

GND

Figure 18: Connection of the serial interfaces
If the voltage of UART is 3.3V, the following reference circuits are recommended. If the voltage is 3.0V, please
change the resistors in the following figure from 5.6K to 14K.
1K

U A R T 1_T X D
U A R T 1_R X D

U A R T1_R T S

1K
1K

U A R T1_C T S

R XD
TX D
R TS
C TS

U A R T 1_D T R

U A R T1_D C D

G P IO

E IN T

5.6K

GND

U A R T1_R I
GND

5.6K

G P IO

D TE
(3.3V )

M odule
Figure 19: Resistor matching circuit

If the voltage of UART is 3V or3.3V, the following reference circuits are recommended:
10K

V D D _E X T
U A R T 1_R X D

TX D

U A R T 1_T X D

RXD
10K

G ND

M odule

D TE

Figure 20 : Diode isolation circuit
Note: please make sure the minimum of client high limit should be less than 2.8V minus the diode drop.
If the voltage of UART is 5V, the following reference circuits are recommended:

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V D D _E X T

M odule

D TE
VDD

4.7K
V D D _E X T

4.7K

47K

RXD

U A R T 1_T X D

Figure 21: TX level matching circuit

V D D _E X T

M odule

D TE

V D D _E X T

VD D

4.7K
4.7K

47K
TX D

U A R T 1_R X D

Figure 22: RX level matching circuit
4.5.3

Debug Interface

SIM800C could achieve software debug function through USB interface. When powering on the module,
connect USB_VBUS, USB_DP, USB_DN, and GND to PC, then install the driver following the prompts, a
UART port could be recognized by PC, customer could achieve the software Debug with this UART port.
SIMCom recommended the following connected diagram:

VBU S

U S B _V B U S
22 R

U SB _ D N

U SB _ D N
22R

U S B _D P

U SB _ D P
1uF

GND

G ND

M O D U LE

U SB

Figure 23: USB reference circuit
The TVS on USB data line should be less than 5pF, and traced by differential forms.
Note: please reserve the USB interface or test point for the further debugging
Table 10: USB_VBUS operation voltage
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Min

Typ

Max

Unit

USB_VBUS

4.3

5.0

7.0

4.5.4

Software Upgrade

Customer could upgrade module’s firmware through USB or UART interface.
If upgrading through USB interface, it is necessary to power on SIM800C first, and then connect USB_VBUS,
USB_DP, USB_DN, and GND to PC. There is no need to operate PWRKEY pin in the whole procedure, when
SIM800C detects USB_VBUS and could communicate normally with USB_DP and USB_DN, it will enter USB
download mode automatically.
If customer upgrades the software through UART interface, it is strongly recommended to lead the UART1_TXD,
UART1_RXD, GND and PWRKEY pin to IO connector for the upgrading, and PWRKEY pin should connect to
GND while upgrading. Refer to the following figure for debugging and upgrading software.

M odule(D C E )

I/O C onnector

S erialP ort
U A R T 1_T X D

TX D

U A R T 1_R X D

R XD

GND

PW R KEY

Figure 24: Connection for software upgrading and debugging
The UART interface supports the CMOS level. If customer connects the module to the computer, the level shifter
should be added between the DCE and DTE.

4.6. UART1_RI Behaviors
Table 11: RI behaviors
State

RI response

Standby

High

Voice call

The pin is changed to low. When any of the following events occur, the pin will be changed to
high:
（1）Establish the call
（2）Hang up the call

SMS

The pin is changed to low, and kept low for 120ms when a SMS is received. Then it is changed
to high.

Others

For more details, please refer to document [2].

The behavior of the RI pin is shown in the following figure when the module is used as a receiver.

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RI

H IG H

E stablish the call
H ang up the call
LO W
Idle

R ing

Figure 25: UART1_RI behaviour of voice calling as a receiver

H IG H

RI
120m s

LO W
Idle

R eceive S M S
URC

Figure 26: UART1_RI behaviour of URC or receive SMS

However, if the module is used as caller, the UART1_RI will remain high. Please refer to the following figure.
H IG H

LO W
R ing

Idle

E stablish
the call

H ang up
the call

Idle

Figure 27: UART1_RI behaviour as a caller

4.7. Audio Interfaces
SIM800C provides an analog input (MICP; MICN), which could be used for electret microphone. The module
also provides an analog output (SPKP; SPKN).
Table 12: Audio interface definition

Pin name

Pin number

Function

MICP

Audio input positive

MICN

Audio input negative

SPKP

Audio output positive

SPKN

Audio output negative

SPKP/SPKN output can directly drive 32Ω receiver.
AT command “AT+CMIC” is used to adjust the input gain level of microphone. AT command “AT+SIDET”
is used to set the side-tone level. In addition, AT command “AT+CLVL” is used to adjust the output gain level.
For more details, please refer to document [1].
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In order to improve audio performance, the following reference circuits are recommended. The audio signals
have to be layout according to differential signal layout rules as shown in following figures.
4.7.1.

Speaker Interfaces Configuration

C lose to speaker

10pF

33pF

10pF

33pF

10pF

33pF

10pF

33pF

10pF

33pF

10pF

33pF

ESD

SPKP

SPKN

M odule

ESD

Figure 28: Speaker reference circuit
4.7.2.

Microphone Interfaces Configuration

These components should
be placed to microphone
as close as possible

M IC P

M IC N

10pF

33pF

The lines in bold type should
be accorded to differential 10pF
signal layout rules

33pF

10pF

33pF

M odule

ESD

Electret
Microphone

Figure 29: Microphone reference circuit
4.7.3.

Audio Electronic Characteristic

Table 13: Microphone input characteristics
Parameter

Min

Typ

Max

Unit

Microphone biasing voltage

1.9

2.2

Working current

2.0

Input impedance(differential)

KΩ

Idle channel noise

-67

dBm0

SINAD

Input level:-40dBm0

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Input level:0dBm0

Table 14: Audio output characteristics
Parameter

Conditions

Min

Typ

Max

Unit

Normal output

RL=32 Ω receiver

4.7.4.

TDD

Audio signal could be interferenced by RF signal. Coupling noise could be filtered by adding 33pF and 10pF
capacitor to audio lines. 33pF capacitor could eliminate noise from GSM850/EGSM900MHz, while 10pF
capacitor could eliminate noise from DCS1800/PCS1900Mhz frequency. Customer should develop this filter
solution according to field test result.
GSM antenna is the key coupling interfering source of TDD noise. Thereat, pay attention to the layout of audio
lines which should be far away from RF cable, antenna and VBAT pin. The bypass capacitor for filtering should
be placed near module and another group needs to be placed near to connector.
Conducting noise is mainly caused by the VBAT drop. If audio PA was powered by VBAT directly, then there
will be some cheep noise from speaker output easily. So it is better to put big capacitors and ferrite beads near
audio PA input.
TDD noise has something to do with GND signal. If GND plane is not good, lots of high-frequency noises will
interference microphone and speaker over bypass capacitor. So a good GND during PCB layout could avoid
TDD noise.

4.8. SIM Card Interface
The SIM interface complies with the GSM Phase 1 specification and the new GSM Phase 2+ specification for
FAST 64kbps SIM card. Both 1.8V and 3.0V SIM card are supported. The SIM interface is powered from an
internal regulator in the module.
4.8.1.

SIM Card Application

Table 15: SIM pin definition
Pin name

Pin number

Function

SIM_VDD

Voltage supply for SIM card. Support 1.8V or 3V SIM card

SIM_DATA

SIM data input/output

SIM_CLK

SIM clock

SIM_RST

SIM reset

SIM_DET

SIM card detection

It is recommended to use an ESD protection component such as ST (www.st.com ) ESDA6V1-5W6 or ON
SEMI (www.onsemi.com ) SMF05C. The SIM card peripheral components should be placed close to the SIM
card holder. The reference circuit of the 8-pin SIM card holder is illustrated in the following figure.

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V D D _E X T

M odule

4.7K
M O LE X -91228

S IM _V D D
S IM _R S T
S IM _C LK
S IM _D E T

51Ω
51Ω

S IM _D A T A

51Ω

GND
VC C
VPP
R ST
C LK
I/O
PR ESEN C E G N D
S IM C ard
100nF

22pF

E S D A 6V 1

Figure 30: Reference circuit of the 8-pin SIM card holder
The SIM_DET pin is used for detection of the SIM card hot plug in. Customer can select the 8-pin SIM card
holder to implement SIM card detection function. AT command “AT+CSDT” is used to enable or disable SIM
card detection function. For details of this AT command, please refer to document [1].
If the SIM card detection function is not used, customer can keep the SIM_DET pin open. The reference circuit
of 6-pin SIM card holder is illustrated in the following figure.
S IM C ard

M odule

S IM _V D D
S IM _R S T
S IM _C LK
S IM _D E T

51Ω
51Ω

S IM _D A T A

51Ω

VC C
R ST
C LK

GND
VPP
I/O

C 707 10M 006 512 2

22pF

100nF

E S D A 6V 1

Figure 31: Reference circuit of the 6-pin SIM card holder
4.8.2.

SIM Card Design Guide

SIM card signal could be interferenced by some high frequency signal, it is strongly recommended to follow
these guidelines while designing:








4.8.3.

SIM card holder should be far away from GSM antenna
SIM traces should keep away from RF lines, VBAT and high-speed signal lines
The traces should be as short as possible
Keep SIM card holder’s GND connect to main ground directly
Shielding the SIM card signal by ground well
Recommended to place a 100nF capacitor on SIM_VDD line and keep close to the SIM card holder
Add some TVS which parasitic capacitance should not exceed 50pF
Add 51Ω resistor to (SIM_RST/SIM_CLK/SIM_DATA) signal could enhance ESD protection
Design Considerations for SIM Card Holder

For 8 pins SIM card holder, SIMCom recommends to use Molex 91228.Customer can visit
http://www.molex.com for more information about the holder.

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Figure 32: Molex 91228 SIM card holder
Table 16: Pin description (Molex SIM card holder)
Pin name

Signal

Description

SIM_VDD

SIM card power supply

SIM_RST

SIM card reset

SIM_CLK

SIM card clock

GND

Connect to GND

GND

Connect to GND

VPP

Not connect

SIM_DATA

SIM card data I/O

SIM_DET

Detect SIM card presence

For 6-pin SIM card holder, SIMCom recommends to use Amphenol C707 10M006 512 .Customer can visit
http://www.amphenol.com for more information about the holder.

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Figure 33: Amphenol C707 10M006 512 SIM card holder
Table 17: Pin description (Amphenol SIM card holder)
Pin name

Signal

Description

SIM_VDD

SIM card power supply

SIM_RST

SIM card reset

SIM_CLK

SIM card clock

GND

Connect to GND

VPP

Not connect

SIM_DATA

SIM card data I/O

Note: Every time plug SIM card interval advice is greater than 2s. Otherwise may not be able to correct
detection.

4.9. ADC
Table 18: Pin definition of the ADC
Pin name

Pin number

Description

ADC

Analog voltage input

SIM800C provides an auxiliary ADC, which can be used to measure the voltage. Customer can use AT command
“AT+CADC” to read the voltage value. For details of this AT command, please refer to document [1].
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Table 19: ADC specification
Parameter

Min

Typ

Max

Unit

Voltage range

2.8

ADC Resolution

bits

Sampling rate

1.0833

MHz

ADC precision

4.10. Network Status Indication
Table 20: Pin definition of the NETLIGHT
Pin name

Pin number

Description

NETLIGHT

Network Status Indication

The NETLIGHT pin can be used to drive a network status indication LED. The status of this pin is listed in
following table:
Table 21: Status of the NETLIGHT pin
Status
Off
64ms On/ 800ms Off
64ms On/ 3000ms Off
64ms On/ 300ms Off

SIM800C behavior
Powered off
Not registered the network
Registered to the network
GPRS communication is established

Reference circuit is recommended in the following figure:
VBAT

M odule
N E T LIG H T

4.7K

47K

Figure 34: Reference circuit of NETLIGHT
4.10.1. NETLIGHT Multiplexing Function
Table 22: NETLIGHT multiplexing function
Pin name

Pin number

Mode 0(default)

Mode 1

NETLIGHT

GPIO

Note: Multiplexing function need different software supply.
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4.11. Operating Status Indication
The pin42 is for operating status indication of the module. The pin output is high when module is powered on,
and output is low when module is powered off.
Table 23: Pin definition of the STATUS
Pin name

Pin number

Description

STATUS

Operating status indication

Note: For timing about STATUS, please reference to the chapter “4.2 power on/down scenarios”
4.11.1. STATUS Multiplexing Function
Table 24: STATUS multiplexing function
Pin name

Pin number

Mode 0(default)

Mode 1

STATUS

GPIO

Note: Multiplexing function need different software supply.

4.12. RF Synchronization Signal
The synchronization signal is used to indicate incoming GSM burst.
Table 25: Definition of the RF_SYNC pin
Pin name

Pin number

Description

RF_SYNC

Transmit synchronization signal

The timing of the synchronization signal is shown below.
220us

577us

T ransm it burst

R F _S Y N C

Figure 35: RF_SYNC signal during transmit burst
4.12.1. RF_SYNC Multiplexing Function
RF_SYNC can also be used as GPIO to indicate the RF Jamming. The RF_SYNC function and RF Jamming
Detection function can be switched by AT+SJDR command.
Table 26: RF_SYNC Multiplexing function

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Pin name

Pin number

Mode 0(default)

Mode 1

RF_SYNC

RF Synchronization Signal

JD（RF jamming detection）

Note: About AT+SJDR, please refer to document [1].

4.13. Antenna Interface
There are two antenna interfaces, GSM_ANT and BT_ANT.
 The input impendence of the antenna should be 50Ω, and the VSWR should be less than 2.
 It is recommended that the GSM antenna and the BT antenna should be placed as far as possible.
 The isolations of the two antenna should be bigger than 30dB
NOTE：About the RF trace layout please refer to“AN_SMT Module_RF_Reference Design_Guide”.
4.13.1 GSM Antenna Interface
SIM800C provides a GSM antenna named GSM_ANT, customer could use 50Ω microstrip line or stripline
antenna connect to the module.
It is recommended to reserve the matching circuit as following:
GND
(P in31)

M odule

G SM
A ntenna

R F connector
G S M _A N T
(P in33)

R 101
C 101

C 102

GND
(P in33)

Figure 36: GSM antenna matching circuit
R101，C101，C102 are the matching circuit, the value should be defined by the antenna design. Normally R101 is
0Ω, C101 and C102 are not mounted.
The RF connector is used for conduction test. If the space between RF pin and antenna is not enough, the
matching circuit should be designed as in the following figure:
GND
(P in31)

M odule

G S M _A N T
(P in33)

G SM
A ntenna

R 101
C 101

C 102

GND
(P in33)

Figure 37: GSM antenna matching circuit without RF connector

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Normally R101 is 0Ω, C101 and C102 are not mounted.
4.13.2 Bluetooth Antenna Interface
It is recommended to reserve the matching circuit as following:
G ND
(P in19)

M odule

BT
A ntenna

R 201

B T _A N T
(P in20)
C 201

C 202

GND
(P in21)

Figure 38: Bluetooth antenna matching circuit
R201, C201, C202 are the matching circuit, the value should be defined by the antenna design. Normally R201 is
0R, C202 and C201 are not mounted.
There are some suggestions for placing components and RF trace for GSM_ANT/BT_ANT:
 The RF connector is used for conducted test, so keep it as close to pin GSM_ANT as possible;
 Antenna matching circuit should be close to the antenna;
 Keep the RF traces impedance as 50Ω;
 The RF traces should be kept far away from the high frequency signals and strong interference
source.

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5. PCB Layout
This section will give some guidelines on PCB layout, in order to eliminate interfere or noise.

5.1

Pin Assignment

Before PCB layout, we should learn about pin assignment in order to get reasonable layout with so many
external components. Following figure is the overview of pin assignment of the module.
STATUS

NETLIGHT

VDD_EXT

PWRKEY

ADC

GND

VBAT

UART1_TXD

GND

UART1_RXD

GSM_ANT

VBAT
UART1_RTS

GND

UART1_CTS

GND

UART1_DCD

RF_SYNC

UART1_DTR

VRTC

UART1_RI

GND

UART

SIM800C

AUDIO

SIM CART

TOP VIEW
USB
GND

USB_DM

MICP

USB_DP

MICN

USB_VBUS

SPKP

UART2_RXD

SPKN

UART2_TXD

ANTANA

GND

SIM_DET

SIM_DATA

SIM_CLK

SIM_RST

SIM_VDD

GND

20
BT_ANT

GND

OTHERS

21
GND

Figure 39: Pin assignment

5.2

Principle of PCB Layout

During layout, attention should be paid to the following interfaces, like Antenna, power supply, SIM card
interface, audio interface, and so on.

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5.2.1

Antenna Interface




5.2.2

Power Supply






5.2.3





SIM card holder has no anti-EMI component inside. Thus SIM card interface maybe interfered,
please pay more attention on this interface during layout;
Ensure SIM card holder is far way from antenna or RF cable inside;
Put SIM card holder near the module, as nearer as possible;
Add ESD component to protect SIM_CLK, SIM_DATA, SIM_RST and SIM_VDD signals which
should be far away from power and high-speed-frequency signal.

Audio Interface



5.2.5

Not only VBAT but also return GND are very important in layout;
The positive line of VBAT should be as short and wide as possible;
The correct flow from source to VBAT pin should go though Zener diode then huge capacitor;
Pin 36 and Pin37 are GND signals, and shortest layout to GND of power source should be designed;
There are 10 GND pads in the module; these pads could enhance the GND performances. On the
upper layer of these pads, do not trace any signal if possible.

SIM Card Interface


5.2.4

The length of trace between pin output and connector should be as short as possible;
Do not trace RF signal over across the board;
The RF signal should be far away from SIM card, power ICs.

The signal trace of audio should far away from antenna and power;
The audio signal should avoid to parallel with VBAT trace.

Others


It is better to trace signal lines of UART bunched, as well as signals of USB.

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6. Electrical, Reliability and Radio Characteristics
6.1

Absolute Maximum Ratings

The absolute maximum ratings stated in following table are stress ratings under non-operating conditions.
Stresses beyond any of these limits will cause permanent damage to SIM800C.
Table 27: Absolute maximum ratings
Symbol

Min

Typ

Max

Unit

VBAT

4.5

Current

2.0

USB_VBUS

II*

IO*

These parameters are for digital interface pins, GPIO, and UART.

6.2

Recommended Operating Conditions

Table 28: Recommended operating conditions
Symbol

Parameter

Min

Typ

Max

Unit

VBAT

Power supply voltage

3.4

4.0

4.4

TOPER

Operating temperature

-40

+25

+85

℃

TSTG

Storage temperature

-45

+90

℃

6.3

Digital Interface Characteristics

Table 29: Digital interface characteristics
Symbol

Parameter

Min

Typ

Max

Unit

VIH

High-level input current

2.1

3.1

VIL

Low-level input current

-0.3

0.7

VOH

High-level output voltage

2.4

VOL

Low-level output voltage

0.4

Note: These parameters are for digital interface pins, such as keypad, GPIO and UART.

6.4

SIM Card Interface Characteristics

Table 30: SIM card interface characteristics
Symbol

Parameter

Min

Typ

Max

Unit

IIH

High-level input current

-1.0

1.0

IIL

Low-level input current

-1.0

1.0

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VIH

High-level input voltage

VIL

Low-level input voltage

VOH

High-level output voltage

VOL

Low-level output voltage

6.5

1.4

2.4

0.27

0.4

1.62

2.7

0.36

0.4

Parameter

Min

Typ

Max

Unit

Output voltage

3.0

1.8

SIM_VDD Characteristics

Table 31: SIM_VDD characteristics
Symbol
VO
IO

6.6

Output current

VDD_EXT Characteristics

Table 32: VDD_EXT characteristics
Symbol

Parameter

Min

Typ

Max

Unit

Output voltage

2.7

2.8

2.9

Output current

6.7

VRTC Characteristics

Table 33: VRTC characteristics
Symbol

Description

Min

Typ

Max

Unit

VRTC-IN

VRTC input voltage

1.2

2.8

3.0

IRTC-IN

VRTC input current

3.0

5.0

VRTC-OUT

VRTC output voltage

2.8

IRTC-OUT

VRTC output current

2.0

6.8

Current Consumption (VBAT=4.0V)

Table 34: Current consumption
Symbol

Parameter

Conditions

Min

Voltage

Typ

Max

4.0

Unit
V

Power drop

PCL=5

350

Voltage ripple

PCL=5
@ f<200kHz

VBAT

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@ f>200kHzss

IVBAT

Average currnet

IMAX

Peak current

2.0

150

Power off mode

130

Sleep mode (AT+CFUN=1)：
( BS-PA-MFRMS=9 )
( BS-PA-MFRMS=5)
( BS-PA-MFRMS=2)

0.88
1
1.5

mA
mA
mA

Idle mode (AT+CFUN=1)：
GSM850
EGSM900
DCS1800
PCS1900

13.8
13.8
13.8
13.8

mA
mA
mA
mA

209
211

mA
mA

126
413

mA
mA

Data mode GPRS (1Rx,4Tx)：
GSM850
EGSM900
DCS1800
PCS1900

394
416
271
285

mA
mA
mA
mA

Data mode GPRS (3Rx,2Tx)：
GSM850
EGSM900
DCS1800
PCS1900

323
330
212
227

mA
mA
mA
mA

Data mode GPRS (4Rx,1Tx)：
GSM850
EGSM900
DCS1800
PCS1900

213
210
150
162

mA
mA
mA
mA

Voice call (PCL=5)：
GSM850
EGSM900
Voice call (PCL=0)：
DCS1800
PCS1900

During Tx burst

2.0

Note: In above table the current consumption value is the typical one of the module tested in laboratory. In the
mass production stage, there may be differences among each individual.

6.9

Electro-Static Discharge

SIM800C is an ESD sensitive component, so attention should be paid to the procedure of handling and
packaging. The ESD test results are shown in the following table.
Table 35: The ESD characteristics (Temperature: 25℃, Humidity: 45 %)
Pin name

Contact discharge

Air discharge

VBAT

±5KV

±12KV

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GND

±6KV

±12KV

UART1_TXD /UART1_RXD

±4KV

±8KV

Antenna port

±5KV

±10KV

SPKP/SPKN/MICP/MICN

±4KV

±8KV

PWRKEY

±4KV

±8KV

6.10 Radio Characteristics
6.10.1 Module RF Output Power
The following table shows the module conducted output power, it is followed by the 3GPP TS 05.05 technical
specification requirement.
Table 36: GSM850 and EGSM900 conducted RF output power
GSM850,EGSM900
PCL

Tolerance (dB) for conditions

Nominal output power (dBm)

Normal

Extreme

±2

±2.5

±3

±4

±3

±4

±3

±4

±3

±4

±3

±4

±3

±4

±3

±4

±3

±4

±3

±4

±3

±4

±5

±6

±5

±6

±5

±6

19-31

±5

±6

Table 37: DCS1800 and PCS1900 conducted RF output power
DCS1800,PCS1900
PCL

Tolerance (dB) for conditions

Nominal output power (dBm)

Normal

Extreme

±2

±2.5

±3

±4

±3

±4

±3

±4

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±3

±4

±3

±4

±3

±4

±3

±4

±3

±4

±5

±4

±5

±4

±5

±4

±5

±4

±5

±6

±5

±6

6.10.2 Module RF Receive Sensitivity
The following table shows the module’s conducted receiving sensitivity, it is tested under static condition.
Table 38: Conducted RF receive sensitivity
Frequency

Receive sensitivity（Typical）

Receive sensitivity(Max)

GSM850,EGSM900

< -109dBm

< -107dBm

DCS1800,PCS1900

< -109dBm

< -107dBm

6.10.3 Module Operating Frequencies
The following table shows the module’s operating frequency range; it is followed by the 3GPP TS 05.05
technical specification requirement.
Table 39: Operating frequencies
Frequency

Receive

Transmit

GSM850

869

～ 894MHz

824

～ 849MHz

EGSM900

925

～ 960MHz

880

～ 915MHz

DCS1800

1805 ～ 1880MHz

1710 ～ 1785MHz

PCS1900

1930 ～ 1990MHz

1850 ～ 1910MHz

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7. Manufacturing
7.1. Top and Bottom View of SIM800C

Figure 40: Top and bottom view of SIM800C

7.2. Typical Solder Reflow Profile

Figure 41: Typical solder reflow profile of lead-free processes

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7.3. The Moisture Sensitivity Level
The moisture sensitivity level of SIM800C module is 3. The modules should be mounted within 168 hours after
unpacking in the environmental conditions of temperature <30℃ and relative humidity of <60% (RH). It is
necessary to bake the module if the above conditions are not met:
Table 40: Moisture sensitivity level and floor life
Moisture Sensitivity Level
(MSL)

Floor Life (out of bag) at factory ambient≤30°C/60% RH or as stated

Unlimited at ≦30℃/85% RH

1 year

4 weeks

168 hours

72 hours

48 hours

24 hours

Mandatory bake before use. After bake, it must be reflowed within the time limit
specified on the label.

NOTES:
For product handling, storage, processing, IPC / JEDEC J-STD-033 must be followed.

7.4. Baking Requirements
SIM800C modules are vacuum packaged, and guaranteed for 6 months storage without opening or leakage under
the following conditions: the environment temperature is lower than 40℃, and the air humidity is less than 90%.
If the condition meets one of the following ones shown below, the modules should be baked sufficiently before
re-flow soldering, and the baking condition is shown in below table; otherwise the module will be at the risk of
permanent damage during re-flow soldering.




If the vacuum package is broken or leakage;
If the vacuum package is opened after 6 months since it’s been packed;
If the vacuum package is opened within 6 months but out of its Floor Life at factory ambient≦30℃
/60%RH or as stated.

Table 41: Baking requirements
Baking temperature

Moisture

Time

40℃±5℃

<5%

192 hours

120℃±5℃

<5%

6 hours

Note: Care should be taken if that plastic tray is not heat-resistant, the modules should be taken out for
preheating, otherwise the tray may be damaged by high-temperature heating.

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8. Appendix
I. Related Documents
Table 42: Related documents
SN

Document name

[1]

SIM800 Series AT Command
Manual

[2]

SIM800 Series UART Port
Application Note_V1 02.doc

[3]

ITU-T
Draft
new
recommendation V.25ter：

Serial asynchronous automatic dialing and control

[4]

GSM 07.07：

Digital cellular telecommunications (Phase 2+); AT command set for
GSM Mobile Equipment (ME)

[5]

GSM 07.10：

Support GSM 07.10 multiplexing protocol

GSM 07.05：

Digital cellular telecommunications (Phase 2+); Use of Data
Terminal Equipment – Data Circuit terminating Equipment (DTE –
DCE) interface for Short Message Service (SMS) and Cell
Broadcast Service (CBS)

[7]

GSM 11.14：

Digital cellular telecommunications system (Phase 2+);
Specification of the SIM Application Toolkit for the Subscriber
Identity Module – Mobile Equipment (SIM – ME) interface

[8]

GSM 11.11：

Digital cellular telecommunications system (Phase 2+);
Specification of the Subscriber Identity Module – Mobile
Equipment (SIM – ME) interface

[9]

GSM 03.38：

Digital cellular telecommunications system (Phase 2+); Alphabets
and language-specific information

[10]

GSM 11.10

Digital cellular telecommunications system (Phase 2)； Mobile
Station (MS) conformance specification； Part 1： Conformance
specification

[11]

AN_Serial Port

[6]

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II. Multiplexing Function
Table 43: Multiplexing function
Pin name

Reset

Pin number

Mode 0(default)

Mode 1

Mode 2

STATUS

I/PD

STATUS

GPIO19

SIM_DET

I/PD

SIM_DET

GPIO20

EINT14

NETLIGHT

I/PD

NETLIGHT

GPIO17

UTXD3

UART1_DTR

I/PD

UART1_DTR

GPIO18

EINT13

UART1_RI

I/PD

UART1_RI

GPIO13

EINT11

UART1_DCD

I/PD

UART1_DCD

GPIO12

URXD3

UART1_CTS

I/PD

UART1_CTS

GPIO14

EINT12

UART1_RTS

I/PD

UART1_RTS

GPIO15

UART1_TXD

GPIO11

UART1_RXD

I/PD

UART1_RXD

GPIO10

UART2_TXD

UART3_TXD

GPIO0

UART2_RXD

I/PD

UART3_RXD

GPIO1

Mode 3

Note: Multiplexing function need different software supply.

III. Terms and Abbreviations
Table 44: Terms and abbreviations
Abbreviation

Description

ADC

Analog-to-Digital Converter

AMR

Adaptive Multi-Rate

Coding Scheme

CTS

Clear to Send

DTE

Data Terminal Equipment (typically computer, terminal, printer)

DTR

Data Terminal Ready

DTX

Discontinuous Transmission

EFR

Enhanced Full Rate

EGSM

Enhanced GSM

ESD

Electrostatic Discharge

ETS

European Telecommunication Standard

Full Rate

GPRS

General Packet Radio Service

GSM

Global Standard for Mobile Communications

Half Rate

Mobile Originated

Mobile Station (GSM engine), also referred to as TE

Mobile Terminated

PAP

Password Authentication Protocol

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PBCCH

Packet Broadcast Control Channel

PCB

Printed Circuit Board

PCL

Power Control Level

PCS

Personal Communication System, also referred to as GSM 1900

PDU

Protocol Data Unit

PPP

Point-to-point protocol

Radio Frequency

RMS

Root Mean Square (value)

Receive Direction

SIM

Subscriber Identification Module

SMS

Short Message Service

Terminal Equipment, also referred to as DTE

Transmit Direction

SINAD

Signal to Noise and Distortion Ratio

UART

Universal Asynchronous Receiver & Transmitter

URC

Unsolicited Result Code

USSD

Unstructured Supplementary Service Data

Phonebook abbreviations
FD

SIM fix dialing phonebook

SIM last dialing phonebook (list of numbers most recently dialed)

Mobile Equipment list of unanswered MT calls (missed calls)

SIM (or ME) own numbers (MSISDNs) list

Mobile Equipment list of received calls

SIM phonebook

Not connect

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IV. Safety Caution

Table 45: Safety caution
Marks

Requirements
When in a hospital or other health care facility, observe the restrictions about the use of mobiles.
Switch the cellular terminal or mobile off, medical equipment may be sensitive to not operate
normally for RF energy interference.
Switch off the cellular terminal or mobile before boarding an aircraft. Make sure it is switched off.
The operation of wireless appliances in an aircraft is forbidden to prevent interference with
communication systems. Forget to think much of these instructions may lead to the flight safety or
offend against local legal action, or both.
Do not operate the cellular terminal or mobile in the presence of flammable gases or fumes. Switch
off the cellular terminal when you are near petrol stations, fuel depots, chemical plants or where
blasting operations are in progress. Operation of any electrical equipment in potentially explosive
atmospheres can constitute a safety hazard.
Your cellular terminal or mobile receives and transmits radio frequency energy while switched on.
RF interference can occur if it is used close to TV sets, radios, computers or other electric
equipment.
Road safety comes first! Do not use a hand-held cellular terminal or mobile when driving a
vehicle, unless it is securely mounted in a holder for hands free operation. Before making a call
with a hand-held terminal or mobile, park the vehicle.
GSM cellular terminals or mobiles operate over radio frequency signals and cellular networks and
cannot be guaranteed to connect in all conditions, for example no mobile fee or a invalid SIM card.
While you are in this condition and need emergent help, please remember using emergency calls.
In order to make or receive calls, the cellular terminal or mobile must be switched on and in a
service area with adequate cellular signal strength.
Some networks do not allow for emergency call if certain network services or phone features are in
use (e.g. lock functions, fixed dialing etc.). You may have to deactivate those features before you
can make an emergency call.
Also, some networks require that a valid SIM card be properly inserted in the cellular terminal or
mobile.

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Contact us:
Shanghai SIMCom Wireless Solutions Co.,Ltd.
Address: Building A, SIM Technology Building, No. 633, Jinzhong Road, Shanghai, P. R. China
200335
Tel: +86 21 3252 3300
Fax: +86 21 3252 3020
URL: www.sim.com/wm

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